Definition: nmcli is a command-line interface used for interacting with NetworkManager, a system network service that manages network connections.

Function: Provides a way to control NetworkManager and report network status directly from the command line.

Features:

 * Configure and manage network interfaces (both wired and wireless).
 * Create, modify, delete, and activate network connections.
 * Display detailed information about network devices and connections.
 * Troubleshoot network issues.

Usage: Commonly used in scripts, automated tasks, and by system administrators who prefer using the command line over graphical tools.

Display the status of all network interfaces:

 ```bash
 nmcli device status
 ```

Connect to a WiFi network:

 ```bash
 nmcli device wifi connect  password 
 ```

List available WiFi networks:

 ```bash
 nmcli device wifi list
 ```

Create a new connection:

 ```bash
 nmcli connection add type ethernet ifname eth0 con-name my-eth0
 ```

Bring down a network interface:

 ```bash
 nmcli device disconnect eth0
 ```

nmcli: Command-line interface for NetworkManager to manage and report network connections and devices.